In the usual photographic process, a silver halide emulsion is exposed to a light pattern, then developed by the application thereto of an alkaline solution of developer, after which a liquid stabilizer or fixer renders the developed image permanent. Such a two step procedure is time consuming. Accordingly, one step processes have been investigated which generally employ a monoweb, that is, a web which may contain developer, alkaline activator for the developer and fixer. The web contacts the exposed silver halide emulsion to accomplish the desired eveloping and fixing in a single step. Such monowebs are subject to deterioration of the developer, since it is in an alkaline environment and therefore subject to atmospheric oxidation. Moreover, reaction between the developer and fixer may occur before use of the monoweb, contributing to a short shelf life.
Other monowebs have been employed which contain only the alkaline activator, while the recording medium comprises a silver halide emulsion directly over which is coated a layer containing both the developer and the fixer. The recording media in such systems are subject to fogging due to premature reaction between the developer and the silver halide. Moreover, reaction between the fixer and developer may occur. Accordingly, the shelf life of such recording madia is short.
Attempts to separate the silver halide, developer and fixer through the use of gelatin layers have been largely ineffective, in part due to difficulties in joining the layers while controlling the effectiveness of the reagents.
It would be desirable to provide a simple one step system having a minimum of components but long shelf life and capability of being carried out rapidly and efficiently on a commercial scale through the use of simple apparatus.
The improved photographic processing system of the present invention and the improved photographic process employing such system satisfy the foregoing needs. The system employs a novel photographic recording medium and a novel processing web. THe medium includes a barrier layer which isolates the silver halide from developer prior to developing. The barrier layer is characterized by being insoluble in water and acidic media but soluble in aqueous alkaline media. The developer is mixed with the barrier material or coated as a separate layer thereon. Since the developer is carried on the recording medium in an acidic environment, it is effectively protected from deterioration. The alkaline activator is carried on the processing web, along with any fixer to be used. When the web contacts the developer, the activator activates the developer and causes penetration of the developer through the barrier layer material to effect the desired development. Fixer from the web then renders the developed image permanent.
Contacting of the developer-containing layer with the processing web can be accomplished through simple automated apparatus using conventional guide rollers, pinch rollers and drive equipment. The processing web usually carries free water so that the activator is an aqueous alkaline solution. However, a free water-yielding material in the web can be used to yield free water on heating or to react with one or more components of the developer layer to release free water and provide the aqueous alkaline activator solution during contacting. Accordingly, the desired photographic processing can be accomplished very simply and effectively. Details of the process and system are set forth in the following specific description and accompanying drawings.
Prior art includes the following U.S. Pat. Nos.: 2,543,181, 2,572,357, 2,992,102, 3,248,219, 3,369,901, 3,468,664, 3,552,971, and T870,007.